Oil and gas pipe measurement specialist Optical Metrology Services (OMS) has completed a pipe measurement and fit-up survey on a critical section of pipeline for the Gorgon Upstream Jansz Scarp Crossing.
The welding of fatigue-sensitive subsea SCR and flowline pipes to tight specifications is critical. This was particularly true during the laying of production pipelines between Barrow Island and the Gorgon and Jansz-Io gas fields in Western Australia.
The critical section of this pipeline crosses the Jansz shelf escarpment, which is considered one of the most significant challenges on the Gorgon project’s offshore scope. This involved laying three pipelines in 200 meters of water at the top of the escarpment down to a water depth of 730 meters. Due to the increased water flow pressures across the escarpment, the 30-inch pipes are highly fatigue-sensitive.
OMS made a pipe measurement and fit-up survey to ascertain which pipes would be suitable for the Jansz Scarp section of the pipeline and in which sequence these pipes should be welded in order to minimise project Hi-Lo.
“In order to prevent bottlenecks during welding and to minimize project delays and risks, OMS captured, recorded and analysed pipe end geometry quickly and accurately,” said Hugh Davies, client solutions director at OMS.
This measurement data was made available to OMS pipe analysis, simulation and fit-up software, SmartFit™, which then calculated the optimum sequence for these pipes before delivery into the bead stall for welding.
Two OMS operators were deployed to Australia September to carry out the onshore inspection of pipes. Using OMS’ PipeChecker™ laser-based measurement tool, the operators measured the geometry of the internal walls of more than 400 pipe ends.
This resulted in about 70 pipes being selected as the most suitable – well within the manufacturing tolerance – for the Jansz Scarp Crossing pipeline. This pipe measurement data was made available to OMS’ SmartFit™ software which calculated the best possible fit-up sequence for the pipes.
For this project, the HiLo requirement was less than or equal to 0.5 mm. The weld seam had to be within 45 degrees of TDC. In addition, the longitudinal weld seams had to be offset to at least 100mm. This data was configured into SmartFit™.
The software analysed the fit-up of the pipes and allowed the operators to mark the best rotational position on each pipe end. In the bead stall, these marks were then aligned to immediately achieve the best rotational position so that misalignment was minimized and the project HiLo was achieved.